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Instrument Flying Handbook
Flight Instruments
Flight Support Systems

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

Flight Support Systems

Attitude and Heading Reference System (AHRS)
As aircraft displays have transitioned to new technology,
the sensors that feed them have also undergone significant
change. Traditional gyroscopic flight instruments have
been replaced by Attitude and Heading Reference Systems
(AHRS) improving reliability and thereby reducing cost and

The function of an AHRS is the same as gyroscopic systems;
that is, to determine which way is level and which way is north.
By knowing the initial heading the AHRS can determine both
the attitude and magnetic heading of the aircraft.

The genesis of this system was initiated by the development
of the Ring-LASAR gyroscope developed by Kearfott located
in Little Falls, New Jersey. [Figure 3-36] Their development
of the Ring-LASAR gyroscope in the 1960s/1970s was
in support of Department of Defense (DOD) programs to
include cruise missile technology. With the precision of
these gyroscopes, it became readily apparent that they could
be leveraged for multiple tasks and functions. Gyroscopic
miniaturization has become so common that solid-state
gyroscopes are found in products from robotics to toys.

Because the AHRS system replaces separate gyroscopes,
such as those associated with an attitude indicator, magnetic
heading indicator and turn indicator these individual systems
are no longer needed. As with many systems today, AHRS
itself had matured with time. Early AHRS systems used
expensive inertial sensors and flux valves. However, today the
AHRS for aviation and general aviation in particular are small
solid-state systems integrating a variety of technology such
as low cost inertial sensors, rate gyros, and magnetometers,
and have capability for satellite signal reception.

Air Data Computer (ADC)
An Air Data Computer (ADC) [Figure 3-37/ is an aircraft
computer that receives and processes pitot pressure, static
pressure, and temperature to calculate very precise altitude,
IAS, TAS, and air temperature. The ADC outputs this
information in a digital format that can be used by a variety
of aircraft systems including an EFIS. Modern ADCs
are small solid-state units. Increasingly, aircraft systems
such as autopilots, pressurization, and FMS utilize ADC
information for normal operations. NOTE: In most modern
general aviation systems, both the AHRS and ADC are
integrated within the electronic displays themselves thereby
reducing the number of units, reducing weight, and providing
simplification for installation resulting in reduced costs.

Analog Pictorial Displays

Horizontal Situation Indicator (HSI)
The HSI is a direction indicator that uses the output from
a flux valve to drive the dial, which acts as the compass
card. This instrument, shown in Figure 3-38, combines the
magnetic compass with navigation signals and a glide slope.
This gives the pilot an indication of the location of the aircraft
with relationship to the chosen course.

Kearfott Attitude Heading Reference System
Figure 3-36. The Kearfott Attitude Heading Reference System (AHRS) on the left incorporates a Monolithic Ring Laser Gyro (MRLG)